Method for optimizing the best resolution of an optical scanning system and apparatus for the same

ABSTRACT

The present invention provides a method and an apparatus for fast finding the best resolution of an optical scanning device during assembling steps. The present invention improves the graphics of the calibration device. Accompanying with calculation of an adjustment device, the present invention generates a referencing parameters. The parameters represent the resolution of the optical scanning device; and further is able to show the balance of horizontal resolution and the balance of vertical resolution. In this case, technicians can optimize the best position of the lens in order to build an optical scanning with precision and narrow the misalignment during assembly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method and an apparatus forfast finding and optimizing the best resolution of an optical scanningdevice.

2. Background Description

Generally, an optical scanning system employs many components such as animage capturing device, lenses and so on, to assemble a scanning modulewith high precision. The scanning module can generate and record animage of an object after proper alignment and calibration. The scanningmodule further would be able to transform the captured image to digitalsignals with carrying out the visual image. In this case, the scanningprocess is completed. Therefore, a precise alignment and good assemblyquality are a very important cause to the scanning module.

In FIG. 1, there is shown a traditional alignment and assembly method ofa scanning module. The scanning module (not shown in FIG. 1) includes atleast a scanning module 10 having a document glass 101, a lens 102 andan image capturing device 103. The image capturing device 103 generallyis a Charged-Coupled Device (CCD). In addition, there are additionalsupporting device needed to assemble a traditional optical scanningsystem, such as calibration device 11, an adjusting device 12 connectedto the image capturing device 103. The adjusting device 12 referencessignals from the image capturing device 103 for displaying parameters orsignals, in order to inform the assembling technicians to identify thestatus of assembly.

Consequently, FIG. 2 shows the schematic demonstration of thecalibration device 11. There is a print 110 on the surface of thecalibration device 11. The print shows multi parallel lines, forcalibration and detection purpose.

Further, please refer to FIG. 3. FIG. 3 shows a char of ModulationTransfer Function (MTF)—Position of the Lens. The MTF is a knownmathematic fiction. If the value of MTF 31 is higher, the resolution ofthe scanning module is greater. On the other hand, lower value of theMTF means lower resolution of the scanning module. The horizontaldimension of the chart represents the position of the lens 32. Usually,the curve 30 of the chart of the MTF-PL will be different for differentscanning module 10. When the researching and developing engineersdetermine which scanning module is implemented, the curve 30 of thechart is fixed. Therefore, for a fixed shape of the chart of MTF-PL,there is a maximum value for the MTF. In theory, as shown in the figure,the best resolution of the scanning module will be achieved if the lens34 is placed on the point where the value of MTF is the maximum. Inpractice, it is very difficult to assemble the scanning module preciselyhaving the best resolution, namely, making the position of lens in thepoint where the MTF achieves the maximum value, due to the misalignment.Thus, if the value of the MITF can be set above a certain level, theresolution of the scanning module is acceptable by the user. In FIG. 3,if the point where the lens is placed is in the tolerant range 36, thevalue of the MTF of the scanning module will be kept above the MTFtolerant value 35. In view of the above, the position of the lens is themajor issue of the resolution of an optical scanning device.

Accordingly, the assembly of the traditional optical scanning deviceincludes the steps of the followings. Firstly, the assembling technicianmounts the document glass 101 and the image capturing device 103. Thelens 102 is able to move along a specified direction linearly, as shownin FIG. 1. The lens is further temporarily fixed in a predeterminedposition. A calibration device 11 is placed on the document glass 101.The calibration device 11 contains a print 110. Pleas refer to FIG. 2.The optical scanning device further includes a light source (not shownin the figure). The light source provides a light illuminated on thedocument glass 101 and later reflected by the calibration device 11. Thelight is transmitted via an optical route 104 to the lens 102, andgenerated an image on the image capturing device 103. The imagecapturing device 103 generates digital signals. In this point, theadjusting device 12 calculates the MTF by referencing the digitalsignals and displays the result. In this case, the value of MTF presentsthe resolution of the calibration device 11, which is placed in thedocument glass 101. The assembling technician is therefore able toadjust the position of the lens in order to get the maximum value ofMTF, and fixes the lens at the position where the value of MTF ismaximum or above the MTF tolerant value. If the value of MTF is maximum,the best resolution of the optical scanning device is achieved.

The calibration device 110, described in the above for adjusting thescanning system, only has one print, and the print contains pluralparallel lines. The vector on X-axis and the vector on Y-axis of thelines give the adjusting device 12 basis to calculate the value of MTFfor representing the resolution of the X-axis and Y-axis. Moreover, somecalibration devices only provide plural parallel lines in one direction,such as X-axis or Y-axis. In this case, the assembling technician onlyget the reference resolution in one direction. Practically, due to themisalignment of the assembly, the axis of the lens 102 is usually unableto be perpendicular to the document glass. Thus, the axis of the lenshas an inclined angular with the X-axis or Y-axis, as shown in FIG. 4A.Upmost, there are possibly containing two inclinations along X-axis andY-axis. In this case, the X-axis resolution and the Y-axis resolution ofthe same point are different. Therefore, the best position of the lenscannot be obtained in this respect. Since a standard resolution can beobtained via traditional skills, the quality of assembled scanningdevices would be reduced if the position of the lens only relies on onedirection, such as X-axis or Y-axis.

In view of the above, it is important to provide a method and anapparatus for optimizing the best resolution of an optical scanningdevice in this industry.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand an apparatus for fast finding the best resolution of an opticalscanning device in order to speed up and simplify the assemblingprocesses.

It is another object of the present invention to provide a simplifiedassembling process in order to increase the product quality and toreduce the cost of the optical scanning device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects and advantages will be betterunderstood from the following detailed description of a preferredembodiment of the invention with reference to the drawings, in which:

FIG. 1 is a schematic demonstration of a traditional scanning module;

FIG. 2 is a schematic demonstration of a calibration device;

FIG. 3 shows a chart of MTF-PL of a scanning module;

FIG. 4A shows the inclination along X-axis direction of a traditionaloptical scanning device;

FIG. 4B shows the inclination along X-axis direction of a traditionaloptical scanning device;

FIG. 5 shows the calibration device of the present invention;

FIG. 6 shows the chat of MTF-PL of the present invention; and

FIG. 7 shows a diagram illustrating assembling processes of the presentinvention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The present invention is directed to an improvement of the print of thecalibration device. By the calculation of the adjusting device, there isgenerated a referencing parameter for fast finding and optimizing thebest position of the lens. In this case, a high precise assemblingprocess is obtained and thus reduces the misalignment caused bydifferent technicians with different skills.

Please refer to FIGS. 5 and 6. FIG. 5 shows the calibration device ofthe present invention. The X-axis direction is along horizontaldirection shown in the lower-left position of FIG. 5. The Y-axisdirection is along vertical direction. The calibration device 5 has anXR print 51. The print 51 contains a plurality of parallel perpendicularlines. When the technicians apply an adjusting device for assembling,the adjusting device will generate a parameter X_(R) for representingthe right side of the horizontal resolution. The value of X_(R) willvary with different positions of the lens, shown as XR curve 61 of FIG.6. In addition, the calibration device further has a YR print. The YRprint contains a plurality of inclined parallel lines. The inclinationangular is between zero and forty-five degrees from the horizontaldirection. In this case, the adjusting device will generate a value ofright side of MTF, denoted as legend Y_(R). The value of Y_(R)represents the right side of the vertical resolution. The value of Y_(R)varies with different positions of the lens, shown as the YR curve 62 inthe FIG. 6. Accordingly, the calibration device has an XL print and a YLprint. The adjusting device is able to generate a left horizontal MTFvalue and a left vertical MTF value by the XL and YL prints, denoted asX_(L) and Y_(L). The X_(L) and Y_(L) represents the left side horizontalresolution and the left side vertical resolution.

When the calibration device receive the parameters X_(R), Y_(R), X_(L)and Y_(L), a total value of MTF, denoted as A, is generated asA=X_(R)+X_(R)+X_(L)+Y_(L). The legend A represents the total resolutionof the scanning module. Larger value of A means better resolution.

Further, regarding the precision during assembly, the lens may inclinealong left and right directions or along front and rear directions. Inthis case, the resolution may be unable to be balanced. In order toovercome the above problems, a horizontal balance value is generated as|X_(R)−X_(L)|. Smaller |X_(R)−X_(L)| means smaller difference of thehorizontal resolution. Accordingly, the vertical balance value is|Y_(R)−Y_(L)|. Smaller |Y_(R)−Y_(L) |means smaller difference of thevertical resolution. Moreover, a left side of the balance value isconsidered as |X_(L)−Y_(L)|. Smaller |X_(L)−Y_(L)|means smallerdifference between the left side of the vertical resolution and the leftside of the horizontal resolution. A right side of the balance value isconsidered as |X_(R)−Y_(R)|. Smaller |X_(R)−Y_(R)| means smallerdifference between the right side of the vertical resolution and theright side of the horizontal resolution. Thus a balance value B of the Mis considered asB=|X_(R)−X_(L)|+|Y_(R)−Y_(L)|+|X_(L)−Y_(L)|+|X_(R)−Y_(R)|. The value ofB represent the sum of MTF balance values of the scanning module.Smaller value of B means better balance of the scanning module.

In view of the above, C is considered as a referencing parameter whichis calculated as C=A−B. Larger C means better resolution and betterbalance of the scanning module.

The adjusting device further provides a display for displaying theparameters described in the above. The displaying method could be adigital type. The assembling technicians can reference the value of theparameters by the help of the display, during the assembling process.The displaying method could be a light indicating type. The technicianscan reference the light in order to determine whether the parametersachieve the optimizing values. In this cases, the parameters can improvethe assembling quality, regarding the resolution.

According to the calibration device and the adjusting device mentionedin the above, the method of the present invention for optimizing thebest resolution is described as follows. Please refer to FIG. 7. FIG. 7shows the diagram of the assembling processes. An assembling technicianfirst fixes positions of an image capturing device and a document glassin predetermined positions. Further, a lens is positioned between theimage capturing device and the document glass, maintaining movablestatus, as step 71. In step 72, a calibration device is placed on thedocument glass; and an adjusting device is connected to the imagecapturing device. The adjusting device is able to read values of a rightside of horizontal MTF, a right side of vertical MTF, a left side ofhorizontal MTF and a left side of vertical MTF as shown in step 73. Instep 74, the adjusting device is able to generate a adjusting parameterby referencing the values of the right side of horizontal MTF, the rightof vertical MTF, the left side of horizontal MTF and the left side ofvertical MTF. Consequently, the assembling technician adjusts theposition of the lens and pay attention to the variances of the adjustingparameter, as illustrated in step 75. In step 76, the technician canobserve the weather the adjusting parameter achieves the maximum value.If the adjusting parameter does not achieve the maximum value, theprocess will back to step 75. However, if the adjusting parameterachieves the maximum, the technician will fix the position of the lens,shown as step 77. In this case, the assembling processes are completed.

Although preferred embodiments of the present invention have beendescribed in the forgoing description and illustrated in theaccompanying drawings, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications, and substituting of parts and elementswithout departing from the spirit and scope of the invention.Accordingly, the present invention is intended to encompass suchrearrangements, modifications, and substitutions of parts and elementsas fall within the scope of the appended claims.

1. A method for optimizing the best resolution of an optical scanningdevice, said method employed in assembling processes for enabling anassembling technician to find the best an acceptable resolution, saidoptical scanning device including at least an image capturing device, alens and a document glass, with support of a calibration device and anadjusting device, said method comprising the steps of : (1) fixing saidimage capturing device and said document glass in a predeterminedposition, said lens is movable between said image capturing device andsaid document glass; (2) placing said calibration device on saiddocument glass and connecting said adjusting device to said imagecapturing device; (3) reading values of a right side horizontal MTF, aright side vertical MTF, a left side horizontal MTF and a left sidevertical MTF from said adjusting device; (4) calculating the values ofsaid right side horizontal MTF, said right side vertical MTF, said leftside horizontal MTF and said left side vertical MTF to generate areferencing parameter, wherein said referencing parameter is displayedin order to inform said assembling technician ; and (5) adjusting theposition of said lens, when the value of said referencing parameterachieving a relative big value, fixing said lens, wherein saidreferencing parameter corresponds to a position of the lens and is thesum of the values of said right side horizontal MTF, said right sidevertical MTF, said left side horizontal MTF and said left side verticalMTF.
 2. The method of claim 1, wherein the step(4) of generating, saidreferencing parameter is the difference between a value of a balance MTFand the sum of the values of said right side horizontal MTF, said rightside vertical MTF, said left side horizontal MTF and said left sidevertical MTF.
 3. The method of claim 2, wherein the value of saidbalance MTF is the sum of the absolute value of left side horizontal MTFminus the right side horizontal 1 MTF and the absolute value of leftside vertical MTF minus the right side vertical MTF.
 4. The method ofclaim 2, wherein the value of said balance MTF is the sum of theabsolute value of left side horizontal MTF minus the right side verticalMTF and the absolute value of left side vertical MTF minus the rightside horizontal MTF.
 5. The method of claim 2, wherein the value of saidbalance MTF is the sum of the absolute value of left side horizontal MTFminus the right side horizontal 1 MTF, the absolute value of left sidevertical MTF minus the right side vertical MTF, the absolute value ofleft side horizontal MTF minus the right side vertical MTF and theabsolute value of left side vertical MTF minus the right side horizontalMTF.
 6. The method of claim 1, wherein the step(4) of displaying, saidadjusting device further comprising a display for display displayingsaid referencing parameter.
 7. The method of claim 6, wherein saiddisplay is a digital type display for displaying said referencingparameter.
 8. The method of claim 6, wherein said display is a lightindicating type display for displaying said referencing parameter. 9.The method of claim 1, wherein said image capturing device is acharged-coupled device.
 10. A method for adjusting a resolution of anoptical scanning device, the method comprising: generating values of aright side horizontal Modulation Transfer Function (MTF), a right sidevertical MTF, a left side horizontal MTF and a left side vertical MTFwith an adjusting device; and generating a referencing parametercomprising a sum of the values of the right side horizontal MTF, theright side vertical MTF, the left side horizontal MTF, and the left sidevertical MTF with the adjusting device; wherein the referencingparameter corresponds to a position of a lens of the optical scanningdevice.
 11. The method of claim 10, further comprising: calculating avalue of a balance MTF; and adjusting the reference parameter accordingto the value of the balance MTF.
 12. The method of claim 11, whereincalculating the value of the balance MTF comprises calculating a sum ofan absolute value of a difference between the values of the left sidehorizontal MTF and the right side horizontal MTF and an absolute valueof a difference between the values of the left side vertical MTF and theright side vertical MTF.
 13. The method of claim 11, wherein calculatingthe value of the balance MTF comprises calculating a sum of an absolutevalue of a difference between the values of the left side horizontal MTFand the right side vertical MTF and an absolute value of a differencebetween the values of the left side vertical MTF and the right sidehorizontal MTF.
 14. The method of claim 11, wherein calculating thevalue of the balance MTF comprises calculating a sum of an absolutevalue of a difference between the values of the left side horizontal MTFand the right side horizontal MTF, an absolute value of a differencebetween the values of the left side vertical MTF and the right sidevertical MTF, an absolute value of a difference between the values ofthe left side horizontal MTF and the right side vertical MTF, and anabsolute value of a difference between the values of the left sidevertical MTF and the right side horizontal MTF.
 15. The method of claim11, wherein adjusting the reference parameter comprises calculating adifference between the values of the balance MTF and the referenceparameter.
 16. An apparatus for changing a resolution of an opticalscanning device, the apparatus comprising: a calibration devicecomprising a plurality of images, wherein the calibration device isconfigured to be positioned on a document glass of the optical scanningdevice; and an adjusting device configured to receive image signals froman image capturing device of the optical scanning device, wherein theimage signals are generated from the plurality of images of thecalibration device, generate values of a right side horizontalModulation Transfer Function (MTF), a right side vertical MTF, a leftside horizontal MTF and a left side vertical MTF from the image signals,and generate a referencing parameter comprising a sum of the values ofthe right side horizontal MTF, the right side vertical MTF, the leftside horizontal MTF, and the left side vertical MTF, wherein thereferencing parameter corresponds to a position of a lens of the opticalscanning device.
 17. The apparatus of claim 16, wherein the adjustingdevice is further configured to: calculate a value of a balance MTF; andadjust the reference parameter according to the value of the balanceMTF.
 18. The apparatus of claim 17, wherein the value of the balance MTFcomprises a sum of an absolute value of a difference between the valuesof the left side horizontal MTF and the right side horizontal MTF and anabsolute value of a difference between the values of the left sidevertical MTF and the right side vertical MTF.
 19. The apparatus of claim17, wherein the value of the balance MTF comprises a sum of an absolutevalue of a difference between the values of the left side horizontal MTFand the right side vertical MTF and an absolute value of a differencebetween the values of the left side vertical MTF and the right sidehorizontal MTF.
 20. The apparatus of claim 17, wherein the value of thebalance MTF comprises a sum of an absolute value of a difference betweenthe values of the left side horizontal MTF and the right side horizontalMTF, an absolute value of a difference between the values of the leftside vertical MTF and the right side vertical MTF, an absolute value ofa difference between the values of the left side horizontal MTF and theright side vertical MTF, and an absolute value of a difference betweenthe values of the left side vertical MTF and the right side horizontalMTF.
 21. The apparatus of claim 17, wherein the reference parametercomprises a difference between the values of the balance MTF and thereference parameter.
 22. An apparatus for adjusting a resolution of anoptical scanning device, the apparatus comprising: means for receivingimage signals from an image capturing device of the optical scanningdevice; means for generating values of a right side horizontalModulation Transfer Function (MTF), a right side vertical MTF, a leftside horizontal MTF and a left side vertical MTF from the image signals;and means for generating a referencing parameter comprising a sum of thevalues of the right side horizontal MTF, the right side vertical MTF,the left side horizontal MTF, and the left side vertical MTF; whereinthe referencing parameter corresponds to a position of a lens of theoptical scanning device.
 23. The apparatus of claim 22, furthercomprising: means for calculating a value of a balance MTF; and meansfor adjusting the reference parameter according to the value of thebalance MTF.
 24. The apparatus of claim 23, wherein the value of thebalance MTF comprises a sum of an absolute value of the left sidehorizontal MTF minus the right side horizontal MTF and an absolute valueof the left side vertical MTF minus the right side vertical MTF.
 25. Theapparatus of claim 23, wherein the value of the balance MTF comprises asum of an absolute value of the left side horizontal MTF minus the rightside vertical MTF and an absolute value of the left side vertical MTFminus the right side horizontal MTF.
 26. The apparatus of claim 23,wherein the value of the balance MTF comprises a sum of an absolutevalue of the left side horizontal MTF minus the right side horizontalMTF, an absolute value of the left side vertical MTF minus the rightside vertical MTF, an absolute value of the left side horizontal MTFminus the right side vertical MTF, and an absolute value of the leftside vertical MTF minus the right side horizontal MTF.
 27. The apparatusof claim 23, further comprising means for calculating a differencebetween the balance MTF and the reference parameter.